Hydropneumatic accumulator



1 United States Patent 1 13,s37,357

[72] Inventor Martin Richard Packer Q 2,695,037 11/1954 McCuistion 138/31 19 Buckingham Road, Cheadle Hulme, 2,703,108 3/1955 McCuistion..... 138/31 Cheshire, England 2,748,801; 6/1956 McCuistion 138/31 [21] Appl. No. 734,436 2,764,997 /1956 McCuistion 138/31 [22] Filed June 4, 1968 2,828,760 4/1958 Taylor et al. l38/31X Patented Nov. 3, 1970 3,158,180- 11/1964 138/31 [32] Priority Sept. 15,1967 3,186,681 6/1965 277/117 [33] Great Britain 3,331,117 7/1967 Jacobellis 138/31X [31 42,061/67 Primary Examiner-Martin P. Schwadron 1 Assistant Examiner--Leslie J. Payne [54] HYDRONEUMATIC ACCUMULATOR Attorney-Keriwood Ross and Chester E. Flavin 2 Claims, 3 Drawing Figs. [52]' us. Cl 92/90; 138/30,138/31;277/117 [51] Int. Cl ..F01b 19/00;

1 3/00 F019 21/16 ABSTRACT: The present invention relates to hydropneu- Fleld ofSearch l38/30, 31; matic accumulators f the type comprising a cylinder divided 92/90 277/ 117 by a piston, which is located as a slidable fit,within\the cylin- 56 R r cud der, into a first chamber for containing a compressible fluid 1 e erences I and a second chamber for containing a relatively incompressi- UNITED STATES PATENTS ble fluid. At least part of one of the piston walls which 228,771 6/1880 Meier 138/31 separates the compressible fluid from the relatively incom- 2,317,796 4/1943 Nielebock 138/31 pressible fluid is ofa resiliently deformable material.

4 5 so h l-ss 46 50 S /.50 4a a Pat ng d'f-Nov. 3, i910 3,537,357

Shdet .1- 5:3

IINVENTOR:

MARTIN RlCHARD'PACKER Patentd Nov. 3, 1970 ll) u 8 4 mvsufoa:

. 'MAmm RICHARD PACKER HYDRONEUMATIC ACCUMULATOR The present invention relates to hydropneumatic accumulators and particularly relates to hydropneumatic accumulators of the type comprising a cylinder divided, by a piston located lit! a slidable lit within the cylinder, into a first chamber for containing a compressible fluid and a second chamber for receiving a relatively incompressible fluid, and including ertia, piston-type accumulators are generally rather slow in their response. For this reason, the piston-type hydropneumatic accumulator has, in many cases, been superseded by the bladder-type hydropneumatic accumulator. The present invention seeks to provide a piston-type hydropneumatic accumulator having an improved response to change in the pressure differential between the compressible fluid and the relatively incompressible fluid.

According to the present invention then, there is provided a hydropneumatic accumulator of the type described in which at least part of one of the piston walls which is to separate the compressible fluid from the relatively incompressible fluid is resiliently deformable.

Preferably, the accumulator is provided with a peripheral inlet/outlet for compressible fluid.

Preferably also, the accumulator is capable of being fitted directly in line into a hydraulic system. With previous hydropneumatic accumulators, it was necessary to fit the accumulator in a terminating branch ofthe hydraulic system.

In a preferred form of the present invention, the piston comprises an annular member having a resiliently deformable diaphragm separating said first and second chambers. Preferably, the piston includes a wall, which slopes inwardly on that side of the diaphragm which is to contain the relatively incompressible fluid to prevent the diaphragm being drawn into said means for allowing the relatively incompressible fluid to enter and leave said second chamber. 7

Although the member within which the piston is located has been described as a cylinder, it is to be appreciated that its cross section, and thus that of the piston, need not necessarily be circular although a circular cross section is preferred. The expressions cylinder" and cylindrical", as used in the specification and claiming clauses, are to be construed as including cross sections other than circular.

Hydropneumatic accumulators may be used for a variety of purposes, for example as a source of hydraulic power storage, as a transfer barrier between two fluids, as a method of absorbing fluid shock and/or pulsation, and as a compensator for temperature expansion or leakage.

Conveniently, the piston of the accumulator is provided with chamfered outer walls to cooperate with a deformable annular stop when the accumulator is shut down or upon the collapse of pressure in the hydraulic system, to trap a volume of relatively incompressible fluid of a hydraulic system between the chamfered walls of the piston, the deformable annular stop and the walls of the cylinder of the accumulator. 1

The piston may be formed from two piston parts, one of said piston parts being provided with a member extending inwardly of the mounting of the resiliently deformable material whereby said resiliently deformable material will flex about said member during a part of, but not the whole of, its possible flexing movement.

Preferably also, the outer periphery of the diaphragm is formed with an annular clamping ring or bead which acts as a sealing member.

In one form of the present invention, a compartment is provided separate from said second chamber by a resiliently deformable diaphragm, and means for allowing communication between said compartment and said first chamber.

The invention will now be described further by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic sectional view of one form of a hydropneumatic accumulator of the present invention,

FIG. 2 is a sectional view of one preferred embodiment of the invention, and

FIG. 3 is a sectional view ofa second preferred embodiment ofthe invention.

Referring to FIG. 1, a hydropneumatic accumulator indicated generally as 10 comprises a piston 12 mounted as a slidable fit within a cylinder or housing 14. The piston 12 divides the cylinder 14 into two chambers 16, 18. The chamber 16 has an outlet 20, and the chamber 18 has a port 22 for connection to a hydraulic system (not shown) employing a relatively incompressible fluid e.g. a liquid.

The piston 12 is generally cup-shaped and the open end faces the chamber 18. A resiliently deformable rubber diaphragm 24 is fixed across the open end (or closed end if desired) of the cup-shaped piston 12 by means of a ring 26 thus forming a compartment 28 separated from chamber 18 by the diaphragm 24 and connecting with the chamber 16 via aperture 30. A disc 32 is fixed to the upper side of the diaphragm 24 opposite port 22 and a washer 34 is fixed to the underside of the diaphragm 24 opposite the aperture 30.

In operation, any increase in pressure in the hydraulic system (not shown) is transmitted via port 22 to the chamber 18. The piston 12 does not respond immediately to this increase in pressure and the initial shock is absorbed by deformation of the diaphragm 24. The deformation of the diaphragm is accommodated by the aperture 30 allowing gas to pass therethrough. The piston 12 then begins to move under the increase in pressure in the chamber 18. On decrease in pressure in chamber 18, the diaphragm 24 accommodates the initial shock by deforming towards port 22, before the piston 12 begins to move. I

The diaphragm is prevented from entering the port 22 by the disc 32 and fromentering aperture 30 by washer 34.

It will be appreciated that the accumulator shown in FIG. 1 has been shown somewhat schematically merely to illustrate the invention.

The outlet 20 of the chamber 16 may be connected to a reservoir (not shown) of a compressible fluid, e.g. a gas. It will also be appreciated that many modifications may be made to the accumulator shown in FIG. 1, tag. the diaphragm 24 may be located lower in the cup-shaped portion of the piston 12.

Referring to FIG. 2 of the drawings, a hydropneumatic accumulator 40 is shown as having a cylinder 42 within which a piston 44 is slidably located. On the upper end of cylinder 42 a top plate 46 is located. This plate has at least one radial gallery 48, and a peripheral gallery 50, located therein, and is arranged so that the peripheral gallery 50 opens internally of the cylinder 42. On the upper outer side of the top plate 46, a capping member 52 is located and a three section circlip shown generally as 54 locates in a circumferential groove 56 in the wall of cylinder 42.

Mounted centrally of capping member 52 is a compressibl fluid connector 58 which threade'dly engages top plate 46 and has a passage 60 running axially and internally thereof to ultimately connect with radial and peripheral galleries 48 and 50. The compressible fluid connector 58 may be provided with a seal 62, on the external side thereof.

A D or O ring 64 may additionally be provided intermediate the length of top plate 46.

At the lower end of the cylinder 42, a base plate 66 is arranged, the base plate 66 having two ducts 68 and 70 extending therethrough. On the lower outer side of base plate 66 is arranged a circlip 72 which also locates in a circumferential groove 74 in the wall of cylinder 42.

Intermediate the length of base plate 66, a D or O ring 76 similar to ring 64 is provided.

On the inner side of base plate 66, an annular deformable member 78 of chamfered profile is located, which may for example be made of rubber.

Piston 44 comprises inwardly sloping walls 80, a resiliently deformable diaphragm 82, and an annular clamping ring 84 which is bolted to walls 80 by means of bolts 86, with diaphragm 82 clamped therebetween. The diaphragm 82 is formed with an annular rib formed integrally therewith.

The accumulator described with reference to FIG. 2 operates as follows:

A compressible fluid, e.g. gas, is introduced into cylinder 42 through connector 58 and galleries 48 and 50, until the volume of the cylinder 42 between top plate'46 and the top of the piston 44 is charged to a pressure somewhat less than the value at which the accumulator is designed to operate.

The pressure of the hydraulic system is then increased, but until the pressure at which the accumulator operates is reached, the hydraulic fluid is allowed to circulate in through duct 68, circumferentially of the inner face of the base plate 66 and out of duct 70 in the direction of the arrows shown. The piston 44 then moves vertically within cylinder 42, so exposing the diaphragm 82 to the pressure of the hydraulic system on one side.

When it is desired to shut down the accumulator, or, when the pressure in the hydraulic system is reduced, the piston 44 falls under the pressure of the gas within the cylinder above it.

A ring 90 of the fluid of the hydraulic system substantially triangular in shape is then trapped between a part 91 of the piston wall 80, deformable member 78 and cylinder wall 42, and as the piston 44 moves further downwardly into the member 78, so that entrapped fluid becomes pressurized to a pressure greater than that exerted by the gas. Thus the oil forms an effective gas seal and prevents gas escaping around the periphery of the piston 44.

Should the pressure in the hydraulic system become reduced to a very low or zero value, then the diaphragm 82 is prevented from being sucked through either of the ducts 68, 70 by the inwardly sloping walls 80 of the piston 44 covering the ducts 68, 70 (Le. the piston is in the position shown in FIG. 2).

On the other hand, should the pressure differential be such as to force the piston up to the top of the cylinder 42, the piston will only rise until diaphragm 82 rests against the bottom of the top plate 46, and the annular clamping ring 84 will close the peripheral gallery 50.

Thus a collapse of pressure in either the hydraulic system or the compressible fluid system should not lead to damage of the diaphragm.

In FIG. 3, there is shown an alternative construction in which the piston 44 of the embodiment illustrated in FIG. 2 is replaced by a two-part piston 100. The lower part 102 of the piston 100 is of substantially the same configuration as the lower half of the piston 44, in that it is provided with inwardly sloping walls 104 which cooperate with the annular deformable member 78.

The upper part 106 of the piston 100 is generally the inverse of the lower part 102, and the two parts 102 and 106 define lower and upper diaphragm chambers 108 and 110 respectively. Supported between the two parts 102 and 106 is a preformed diaphragm 112. The diaphragm 112 rests on lower piston part 102 and is retained in position by means of two annular ribs 114 formed integrally with the diaphragm which locate in grooves 116 defined in the upper piston part 106. Three bolts 115 hold the parts 102 and 106 together. D or O ring seals 118 are provided intermediate the length of both piston parts 102 and 104. The upper piston part 106 is provided with a member 119 extending inwardly of the mounting of said diaphragm 112 upon which it is possible for the diaphragm to flex. The base plate 66 is similar to that of FIG. 2 except that an axially extending bore 123 is formed therein which terminates at its lower end in a portion of increased diameter 124. A member 126 of circular cross section is located in the bore 123. A D or O ring 125 is located near to the portion 124 and not only acts as a seal, but also helps to retain the member 126 in position.

A subbase plate 127 is secured to base plate 66 by bolts (not shown). The subplate 127 includes conduits 129, 131 which connect with ducts 68, 70 respectively. The hydraulic system in which the accumulator is-to operate is connected to conduits129, 131.

The top plate 46 is similar to the top plate illustrated in the embodiment of FIG. 2 although the capping member 52 is of somewhat slimmer cross section. In the embodiment of FIG. 3, the compressible fluid connector 58 is in the form of a nonreturn valve, through which it is possible to introduce a charge of compressible fluid into the cylinder 42. A venting valve (not shown) is additionally threadedly engaged into the top plate 46. The venting valve enables the cylinder 42 to be bled of compressible fluid before the capping member is removed when dismantling the accumulator. It will be appreciated that the requirement that the venting valve should be removed before the accumulator can be dismantled acts as a safety feature inasmuch as any compressible fluid pressure is released through the valve before the capping member 52 can be removed.

In operation, the accumulator described with reference to FIG. 3 operates in a manner similar to that previously described. In the shutdown position when the piston lies at the bottom of its travel within the cylinder 42, the diaphragm 112 flexes around the curved portion 117 of lower piston part 102 and the pressure of the compressible fluid causes the diaphragm 112 to deform and occupy the lower diaphragm chamber 108.

In a piston free-floating condition (illustrated in FIG. 3). the diaphragm 112 is able to flex about the curved peripheries of either lower piston part 106 or upper piston part 102, depending upon the pressure differential existing between the compressible and incompressible fluids.

Should the pressure of the incompressible fluid rise in excess of the compressible fluid, then, as previously described, the piston 100 rises to the top of its cylinder 42, such that the upper piston part 102 closes the peripheral gallery 50. The diaphragm 112 flexes about the curved member 119 of the upper piston part 106 and occupies the upper diaphragm chamber 110.

It will be appreciated that, since the diaphragm I12 flexes about the different radii of the curved shoulders of upper and lower piston parts 102 and 106, wear on the diaphragm 112 is considerably reduced thereby extending the life of the diaphragm 112.

The bore 123 and member 126 arranged in base plate 66 act as a safety device when the accumulator is being dismantled. When the bolts (not shown) securing the base plate 66 and subplate 127 together are removed, if any compressible fluid pressure remains in the accumulator, the member 126 is pressed downwardly within the bore 123 by the diaphragm 112 so that the D or O ring 125 allows the member 126 to fall from the base plate 66 and the diaphragm 112 severs on the sharp edges 129 of base plate 66 and compressible fluid pressure is able to escape through the ducts 68 and 70 and the bore 123.

It will be appreciated that many modifications are possible within the scope of the invention, for example the subplate 127 may be used to mount the accumulator. Further, the subplate can be in the form of the capping member 52, located on the top of the accumulator.

It will also be appreciated that a subframe 127 could be attached to the base plate 66 of the embodiment illustrated in FIG. 2.

Iclaim:

1. In a piston-type hydropneumatic accumulator responsive to changes in the pressure differential between a compressible fluid and a relatively incompressible fluid delivered thereto from respective external sources the combination of:

an open-ended housing having a side wall;

a housing-enclosing end wall at each end of the housing;

a piston having an outermost side wall in sleeved relationship to the sidewall of the housing and being bodilyreciprocatable longitudinally therewith;

the piston including a chamber-separating component consisting of a resiliently-deformable diaphragm extending from the side wall of the piston and transversely of the housing and defining on its opposite sides a first compressible fluid accommodating chamber and a second ina side wall portion of'- the piston sloping inwardly on the second chamber side of the diaphragm and upon contact of the side wall portion with the adjacent end wall covering the second inlet/outlet means for the prevention of the diaphragm being drawn into said second inlet/outlet means while permitting circulatory passage of the incompressible fluid between the second inlet/outlet means and respective source.

2. The accumulator as set forth in claim 1, wherein the first 10 inlet/outlet for the compressible fluid includes at least one radially-extending gallery. 

